When performing inspection or assembly and the like on a variety of products, a conventional gripping device has been used to hold or grip work pieces in order to transport or handle the work pieces. The gripping devices have different shapes and sizes depending on the specification of the work piece, and, in general, have a pair of opening and closing lever portions so as to be configured to grip and pluck the work piece using this opening and closing levers.
In the gripping device of this type, such a device with a toggle mechanism is known in which a work piece may be gripped with greater force (gripping force) than the input force to operate a pair of opening and closing lever portions. This toggle mechanism is regarded as a servo or booster mechanism which is capable of increasing the output force larger than the input force.
Gripping devices of a toggle-type like this with a robot hand have been described in Japanese Utility Model Application Publication JP-U-59-160184 A and Japanese Patent Application Publication; JP 2008-364981. This robot hand is mainly comprised of a vertically movable rod portion, an operation piece mounted in the lower end of the rod portion, a pair of connecting levers, one end of each of which is connected to the operation piece through a pin or shaft so as to be rotatable about that end, and a pair of opening and closing lever portions, the upper end of each being rotatably connected to the other end of the pair of connecting lever portions via a pin or shaft.
The pair of opening and closing lever portions is linked at the intermediate location thereof to a case body or housing through a pin or shaft and is made rotatable about this connecting location. In addition, the lower ends of the pair of opening and closing lever portions has a role to act as the claw portion for gripping the sides of the work piece. In addition, the pair of opening and closing lever portions is disposed to face each other with the rod portion and the operation piece interposed, i.e., outwardly of the side of rod portion and operating piece. The pair of opening and closing lever portions is supposed to be set in the open state by rotating, with both upper ends approaching while both lower ends are spaced apart in response to the rod portion being moved downwardly.
When gripping a work piece using a robot hand that is configured in this manner, the rod is moved upward. Then, since the operation piece also moves upward, the pair of connecting levers moves upward while rotating so as to push the upper portions of the pair of opening and closing levers outwardly. Thus, the pair of opening and closing lever portions rotates about the intermediate portion as a support point and begins to close so that the lower ends will be close to each other. As a result, the work piece may be gripped by sandwiching the work piece from both sides. Specifically, since a pair of opening and closing lever portions is configured to open and close by using a toggle mechanism, a work piece may be gripped reliably in a large gripping force.